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China’s Tianwen-1 orbiter has captured rare images of interstellar comet 3I/ATLAS as it passed Mars in early October. Astronomers say the object, discovered on May 7, 2025, came from outside our solar system and released gas and dust as it moved closer to the Sun.
Tianwen-1 photographed the faint comet from about 30 million kilometers away, giving researchers an unusually close look at a visitor that does not belong to our planetary neighborhood.
The comet is only the third confirmed interstellar object ever seen near the Sun. The first was ‘Oumuamua in 2017, which behaved more like a fast-moving rock. The second was Borisov in 2019, which looked and acted like a normal comet. 3I/ATLAS fits the second category.
It contains frozen materials that turn into gas when heated. That process formed a thin cloud and tail, which is what astronomers expect from comets that form around distant stars.
Researchers are interested in objects like this because they may carry unaltered material from faraway solar systems. Studying that material helps scientists compare how planets form in different parts of the galaxy. Instead of sending spacecraft to other stars, these passing objects bring samples close enough for remote observation.
Tianwen-1 took the images with an instrument normally used to map the surface of Mars. Engineers spent weeks running models and tests to make sure the camera could pick up something so dim and distant. Individual images were later combined into an animation that shows the comet’s movement.
Capturing the comet was not easy. It measures roughly 5.6 kilometers across and was far from the orbiter. It was also moving fast. The comet traveled at about 58 kilometers per second, while Tianwen-1 moved at about 86 kilometers per second around Mars. The comet looked tens of thousands of times dimmer than the bright features on Mars, and the final images were grainy but clear enough to confirm the sighting.
Europe’s Mars Express and the ExoMars Trace Gas Orbiter also aimed their cameras at 3I/ATLAS on October 3. Each craft used imaging tools designed for Martian landscapes, not distant comets. Even so, all three missions succeeded. Their teams say these joint results were a rare example of multiple spacecraft observing an interstellar object at the same time.
Interstellar objects remain one of the biggest unanswered questions in astronomy. Experts want to know what they are made of and how common they are. Some may carry organic molecules, which are the building blocks of life. Others may be fragments from disrupted planets or frozen debris left over after stars formed.
Several missions will try to study similar visitors more directly. China’s Tianwen-2 mission plans to study a near-Earth asteroid and then a comet.
The European Space Agency’s Comet Interceptor will wait in space until a fast-moving comet or interstellar object comes close enough to chase. NASA and other agencies have also discussed sending craft designed to catch up with interstellar objects as soon as they are spotted.
If better detection systems pick up more of these objects earlier, scientists may be able to observe them at closer range. What seems rare today could become a routine part of space research in the future.
Source: China’s Tianwen-1 Mars orbiter captures image of interstellar object older than the solar system
